How to capitalize first letter in bash? [duplicate] - bash

Question

This question already has answers here:
uppercase first character in a variable with bash
(17 answers)
Closed 2 years ago.
editAppsDotPy() {
echo 'from django.apps import AppConfig' >> apps.py
echo >> apps.py
echo >> apps.py
echo "class ${APP_NAME}Config(AppConfig):" >> apps.py
echo " name = '${APP_NAME}'" >> apps.py
}
How would you capitalize the variable in the 5th line?
I was trying to do it with ${APP_NAME^} but it returns me an error.

Answer 1

Your function rewritten to work with more various shells:
script.sh:
#!/usr/bin/env sh
capitalize()
{
printf '%s' "$1" | head -c 1 | tr [:lower:] [:upper:]
printf '%s' "$1" | tail -c '+2'
}
editAppsDotPy()
{
cat >> 'app.py' <<EOF
from django.apps import AppConfig
class $(capitalize "$APP_NAME")Config(AppConfig):
name = '$APP_NAME'
EOF
}
APP_NAME='foo'
editAppsDotPy
Demoing:
sh script.sh
cat app.py
Output:
from django.apps import AppConfig
class FooConfig(AppConfig):
name = 'foo'

Answer 2

Assuming that tr is in your path, the more common parameter substitutions can help you too.
Your fifth line could look like the following:
echo "class `tr [:lower:] [:upper:] <<<${APP_NAME:0:1}`${APP_NAME:1}Config(AppConfig):" >> apps.py
I also tested this in zsh 5.8.

Answer 3

If your version of bash is too old to support that extension (Like the OS X version), or you're using a shell like zsh that doesn't support it at all, you have to turn to something else. Personally, I like perl (Which I think OS X comes with):
$ perl -ne 'print ucfirst' <<<"foobar"
Foobar
or for something in the middle of a longer string:
$ foo=bar
$ echo "foo='$(perl -ne 'print ucfirst' <<<"$foo")'"
foo='Bar'
which works in bash and zsh.